It is well-known that red mud, the final waste of the Bayer alumina production, provides great problems all over the world. This material is alkaline and it heavily contaminates when waters leak from red mud storage places--owing to both its alkali and iron oxide content. Furthermore, in dry condition, its fine fly-powder is easily blown away by the wind. The large quantity of red mud also causes problems, since an enormous area is needed for its storage. That is why a number of processes, among them several patents are concerned with the treatment of red mud. For instance, according to FRG Patent No. 1.592.104 solid granules are prepared from red mud which is dissolved in water to be purified. This material consists primarily of iron and aluminum sulfate. Charging of the solid water purifying agent is cumbersome, it dissolves slowly and results in plenty of remaining insoluble precipitate.
With the exception of application No. M1-1055/1987, filed on Apr. 13, 1987, all these processes are, however, single-stage technologies, in the course of which either by-products (waste), or the final product has a large refuse content. Thus, the specific efficiency of the product is small during utilization. In case of multistage, more complex processes, even more waste arises and usually their object is only to recover a single particular target product.